Improvement in steam-engine slide-valves



@niet gaat @eine @une`4 iJAMES HEMPHILL, or PITTSBURG, PENNSYLVANIA.

Letters Patent Ne. 78,205, aerea Mey 26,1868.

IMPROVEMENT IN STEAM-ENGINE SLIDE-VALVES.

TQ ALL WHOM IT MAYCONCRN:

Be it known that I, JAMES HEMPIIILL, of the city of Pittsburg, in the county of Allegheny, and State oi' Pennsylvania, have invented a new and useful Improvement in Balance Slide-Valves; and I do hereby declare the, following to be a full, clear, and exact description thereof, reference being had to the accompanying drawings, making a part of this specification, which shows a longitudinal vertical section of a stcarnfchest and slidevalve fitted with my improved devices for balancing the valve. i Y' The nature of my invention consists in the construction of improved devices for balancing sliding-valves,

' whereby the top of the valve will be almost wholly relieved ofthe pressure otherwise exerted on 'it by -the steam in the steamchest, with a consequent-saving of friction and wear, and a lesseningoi the amount cf power required to operate the valve.

To enable others skilled in the artito make and use my invention, I will proceed to describe its construction andma-nner of use.

v a a represent a steamfchest, which may be of any known construction, and having any desirable number or arrangement of steam-ports, Z1, and exhaust-port, c, by'whieh the steam-chest a is connected with the cylin der. The slide-valve ci, of any known construction, is operated in the usual way, andfor the usual purposes, by` a valve-rod, al', passing through a stalling-box, t2. On the valve d rests a v-alvecover, e, which is properly steadied in its place by braces attached to it at suitable intervals, and which project against the sides'a oi' the chest. A stem, e', extends upward from the valve-cover e, through an opening in the topplate a of thest'camchest. This opening is usually of considerable size. A collar, z', is made on the stern c', on which rests a relief-plate, a, the shape of the plate being such that it will nearly fill the opening loft in the top, a', ofthe steam-chest, its size a little less than the horizontal area of the inside of the valve d, audits upper face being even with the uppe rfa-ce of the top, a. On this is tted a thin metallic packing-disk or diaphragm, s., large enough to'project entirely over and beyond the opening left in the top, a. Its outer edge is held down fast to `the top, a', by a collar, n, which is secured toV the projecting flange n', or held in place in other convenient way. Over the stem e, I pass another plate, o', usually a little less in area than the lower plate o. The plates q o and disk s, I hold rmly down on to the collar and at the same time make a tight joint around the stem e by a nut,f, screwed on to the upper end of the stem. A cover, m, of which the collar n may, ii' desirable, form a part, shuts in the whole, an opening, g, however, bcing left, for the escape ot' any steam which may leak into the upper cavity ot'- tho chest.

The operation of the devices named is, then, as follows: `Steam from the boiler is introduced into the steamy chest a a', and the valve al is operated by it in the usual way. Without any balancing of the valve d, the

steam in the steam-chest would press down uponit with a pressure per square inch equal to the pressure indicated by a correct steam-gauge. This would cause enormous loss from friction, wear and tear, and in the amount of power required to operate the valve. But by the usc ot' a relief-plate, o, attached to the stem e' of the valve-cover c, such plate o being slightly less than the inside horizontal aren. of the valve d, and secured by packing, as described, I remove or balance the greater part of' this downward pressure. The steam exerts a counter-pressure against the plate 0, and thus acts as a lifting-force, tending to lift the cover c o' the valve d. Then the proportion of the force acting upward against the plate o, is to the force acting downward on the valve d, as the area of the plate a is to the area of the inside lof the valve d; and the area ofthe latter 'should always be slightlyin excess of the area of the former, so as to secure asuflicicntprcponderance in the downwardacting pressure to keep the cover e firmly seated on the valve'tZ. By the usc'of these devices I am able to relieve the valve 0l of nearly all thc pressure which thc steam would otherwise exert, andbalance it so perfeetly, that but a very small force is required to give to the valve the throw required in operating the engine.

What I claim as my invention, and desire to secure by Letters-Patent, is- The combination 4of the valve-cover e, with its stem r", and the diaphragm s, and plates o o,arranged suhstantiallyas described for the purpose set forth.

In testimony'whereof I, the saidJAMEs HMPHILL, have hereunto set my hand.

JAS. HEMPHILL. Witnesses: i

WM. F. GRAHAM, G. H. CHRISTY. 

